1. Field of the Invention
The present application has been filed claiming the Paris Convention priority based on the Japanese patent application No. 2006-219484 (filed on Aug. 11, 2006) and the Japanese patent application No. 2007-141544 (filed on May 29, 2007), and a whole of the descriptions of the applications are herein fully incorporated in the description of the present specification by reference.
The present invention relates to a process for producing a prepolymerization catalyst for polymerization of an olefin, and a process for producing an olefin polymer using the same prepolymerization catalyst.
2. Description of the Related Art
As the gas phase polymerization process of an olefin, there is dominantly employed a process for obtaining a particle-like polymer by supplying a solid catalyst and an olefin into a fluidized bed reactor, and polymerizing the olefin on the fluidized bed. This process is known to simplify the production process or to reduce the production cost in comparison with a liquid phase polymerization process, because a polymer precipitation step and a polymer separation step after the polymerization is unnecessary in this process. As such a gas phase polymerization process, there is proposed a process for subjecting an olefin to gas phase polymerization in a fluidized bed reactor, using a so-called prepolymerization catalyst. This prepolymerization catalyst is prepared by prepolymerizing an olefin in the presence of a solid catalyst component in which a catalyst component for polymerization of an olefin is carried on a fine particle support, for example, methylaluminoxane and a metallocene compound carried on silica (cf. JP-A-9-221512).
However, there are disadvantages in this gas phase polymerization of the olefin by using the conventional prepolymerization catalyst obtained by prepolymerizing the olefin in the presence of the above solid catalyst component in which the catalyst component for polymerization of the olefin is carried on the fine particle support: that is, an agglomeration of the particles occurs during the gas phase polymerization and hinders the fluidization of the resulting polyolefin particles and the catalyst particles, which results in inhomogeneous mixing of the particles on the fluidized bed; and such an agglomeration clogs the outlet of the fluidized bed reactor when the polyolefin particles are drawn out of the fluidized bed reactor.
Under such circumstances, an object of the present invention is to provide a process for producing a prepolymerization catalyst for polymerization of an olefin, the use of such a polymerization catalyst being effective to suppress the agglomeration of particles during the gas phase polymerization of the olefin in a fluidized bed reactor, and another object thereof is to provide a process for producing an olefin polymer by using the same prepolymerization catalyst for polymerization of olefin, produced by the above process.